vue-vant组件运用

<script>
    // var vConsole = new VConsole();
    // 定义一个名为 button-icon 返回顶部的新组件
    Vue.component('button-icon', {
        data: function () {
            return {
                btnFlag: false//返回顶部
            };
        },
        mounted() {
            window.addEventListener('scroll', this.scrollToTop);
        },
        destroyed() {
            window.removeEventListener('scroll', this.scrollToTop);
        },
        methods: {
            // 后退
            navGoBack() {
                history.back();
            },
            // 点击图片回到顶部方法，加计时器是为了过渡顺滑
            backTop() {
                const that = this;
                let timer = setInterval(() => {
                    let ispeed = Math.floor(-that.scrollTop / 5);
                    document.documentElement.scrollTop = document.body.scrollTop = that.scrollTop + ispeed;
                    if (that.scrollTop === 0) {
                        clearInterval(timer);
                    }
                }, 16);
            },

            // 为了计算距离顶部的高度，当高度大于60显示回顶部图标，小于60则隐藏
            scrollToTop() {
                const that = this;
                let scrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop;
                that.scrollTop = scrollTop;
                if (that.scrollTop > 90) {
                    that.btnFlag = true;
                } else {
                    that.btnFlag = false;
                }
            }
        },
        template: '<van-icon name="back-top" v-if="btnFlag" class="go-top" @click="backTop"/>'
    });
    //定义一个名为 nav-back 返回上一页导航栏的新组件
    Vue.component('nav-back', {
        methods: {
            // 后退
            navGoBack() {
                history.back();
            }
        },
        template: '<van-nav-bar title="{$titleName}" left-arrow @click-left="navGoBack"></van-nav-bar>'
    });

    //图片超出隐藏
    function onWidthHeight(width, height, obj) {
        if (width > height) {
            obj.style.height = '100%';
        } else {
            obj.style.width = '100%';
        }
    }

    //判断是否是千帆
    function isQianfan() {
        let ua = window.navigator.userAgent.toLowerCase();
        if (ua.toLowerCase().search('qianfan') !== -1) {
            return true;
        } else {
            return false;
        }
    }

    //公共底部标签
    Vue.component('nav-footer-tabbar', {
        data: function () {
            return {
                // active: 0
            };
        },
        methods: {
            qfGoBack(index) {
                qfGoBack();
            }
        },
        template: '<van-tabbar active-color="#1989FA" inactive-color="#000" placeholder="true" >\n' +
            '  <van-tabbar-item @click="qfGoBack()" icon="wap-home-o">返回APP</van-tabbar-item>\n' +
            '</van-tabbar>'
    });

    function qfGoBack(index) {
        QFH5.close();
    }
</script>